A vehicle power supply device as follows has been conventionally proposed. A high-voltage battery is mounted in a vehicle and DC electrical power outputted from the battery is converted to AC electrical power by an inverter to supply electrical power to an accessory socket (see, for example, Japanese Patent Application Publication No. 2004-276672). Mounting the power supply device in the vehicle enables an operation of an electric device in the vehicle. Accordingly, for example, a mobile phone can be charged in the vehicle by connecting a charger of the mobile phone to the power supply device.
However, when the fact that the battery mounted in the vehicle is being discharged to supply electricity to the electric device via the accessory socket is displayed, a user may confuse the display indicating that the battery is being discharged to supply electricity the electric device, with a display indicating that the battery is being charged by using an external power supply or an external charger, and make erroneous recognition.